Disclosed is a dental root canal treatment instrument having a simplified manufacturing process involving manufacturing the work portion and the joint portion by means of the same processing method. A metal rod-form body (11) has a work portion (11a) forming a fine taper which is inserted into the root canal when used, and a joint portion (11b) connected to the thick-diameter end of the work portion and embedded in a handle (12), wherein the work portion and the joint portion are formed by the same processing method. The dental root canal treatment instrument (10) is completed by forming the handle (12) by injecting a synthetic resin to cover the joint portion (11b). The bond between the joint portion and the handle can be reinforced by adding at least one protrusion or recess to the joint.
